This image released by DreamWorks II Distribution Co., LLC and Twentieth Century Fox Film Corporation shows Sally Field and Daniel Day-Lewis appear in a scene from "Lincoln." (AP Photo/DreamWorks II Distribution Co., LLC and Twentieth Century Fox Film Corporation, David James)

The scene: Tehran’s Mehrabad airport, January 1980. Six U.S. diplomats, disguised as a sci-fi film crew, are about to fly to freedom with their CIA escorts. But suddenly there’s a moment of panic in what had been a smooth trip through the airport.

The plane has mechanical difficulties and will be delayed. Will the Americans be discovered, arrested, even killed? CIA officer Tony Mendez, also in disguise, tries to calm them. Luckily, the flight leaves about an hour later.

If you saw the film Argo, no, you didn’t miss this development, which is recounted in Mendez’s book about the real-life operation. That’s because director Ben Affleck and screenwriter Chris Terrio replaced it with an even more dramatic scenario, involving canceled flight reservations, suspicious Iranian officials who call the Hollywood office of the fake film crew (a call answered just in time), and finally a heart-pounding chase on the tarmac just as the plane’s wheels lift off, seconds away from catastrophe.

Crackling filmmaking – except that it never happened. Affleck and Terrio, whose film is an Oscar frontrunner, never claimed their film was a documentary, of course. But still, they’ve caught some flak for the liberties they took in the name of entertainment.

And they aren’t alone – two other high-profile best-picture nominees this year, Kathryn Bigelow’s Zero Dark Thirty and Steven Spielberg’s Lincoln, have been criticized for different sorts of factual issues.

The latest episode involved Lincoln, and the revelation that Spielberg and his screenwriter, the Pulitzer-winning playwright Tony Kushner, took liberties depicting the 1865 vote on the 13th amendment outlawing slavery. In response to a complaint by a Connecticut congressman, Kushner acknowledged he’d changed the details, having two Connecticut congressmen vote against the amendment when, in fact, all four voted for it.

In a statement, Kushner said he had “adhered to time-honored and completely legitimate standards for the creation of historical drama, which is what Lincoln is. I hope nobody is shocked to learn that I also made up dialogue and imagined encounters and invented characters.”

His answer wasn’t satisfying to everyone. New York Times columnist Maureen Dowd called on Spielberg this weekend to adjust the DVD version before it’s released – lest the film leave “students everywhere thinking the Nutmeg State is nutty.”

One prominent screenwriting professor finds the Lincoln episode “a little troubling” – but only a little.

“Maybe changing the vote went too far,” says Richard Walter, chairman of screenwriting at the University of California. “Maybe there was another way to do it. But really, it’s not terribly important. People accept that liberties will be taken. A movie is a movie. People going for a history lesson are going to the wrong place.”

Walter says he always tells his students: “Go for the feelings. Because the only thing that’s truly real in the movies are the feelings that people feel when they watch.”

Carson Reeves, who runs an influential screenwriting website called Scriptshadow, says writers basing scripts on real events face a constant problem: No subject or individual’s life is compelling and dramatic enough by itself, he says, that it neatly fits into a script with three acts, subplots, plot twists and a powerful villain.

“You just have to get rid of things that maybe would have made the story more truthful,” says Reeves, who actually gave the Lincoln script a negative review because he thought it was too heavy on conversation and lacked action.

Of the three Oscar-nominated films in question, Zero Dark Thirty has inspired the most fervent debate. The most intense criticism, despite acclaim for the filmmaking craft involved, has been about its depictions of interrogations, with some, including a group of senators, saying the film misleads viewers for suggesting that torture provided information that helped the CIA find Osama bin Laden.

There also have been questions about the accuracy of the depiction of the main character, a CIA officer played by Jessica Chastain; the real person – or combination of people, according to some theories – that she plays remains anonymous.

To Walter, the screenwriting professor, keeping track of all the details is a losing battle.

“When I am hungry and crave a tuna fish sandwich, I don’t go to a hardware store.” he says. “When I seek a history lesson, I do not go to a movie theater. I loved Argo even though I know there was no last-minute turn-around via a phone call from President Carter, nor were there Iranian police cars chasing the plane down the tarmac as it took off. So what? These conceits simply make the movie more exciting.”